The invention relates to the technical field of surgical instruments for correcting a deformation in the spinal column.
The invention has an especially advantageous application for scoliosis correction.
In the field of spinal osteosynthesis, it is perfectly well known to use pedicle screws having their heads, in the form of sockets, fitted for the assembly and the fastening of at least one connection rod for performing a distraction or a compression, and redefining the curvature.
Different technical solutions have been provided, as for example appears from the teachings of patents FR 2.658.413 and EP 0.699.056.
Whatever the technical solution selected to install the connection rods, it is necessary for the pedicle screw heads to be substantially aligned for the engagement of said rods into recesses in the screw heads.
Now in spine pathologies with a severe deformation type (such as scoliosis), the vertebrae are displaced in the three planes of space: rotation, translation, and tilting.
It thus appears to be necessary to be able to correct such a deformation of the spinal column with the objective of straightening up the vertebrae so that they can be aligned.
Here again, various technical solutions have been provided.
The basic concept of these different solutions is the use of tubes which are temporarily attached to the pedicle screw heads. The different tubes are thus attached perpendicularly to the column axis and are angularly shifted, given the column deformation. The tubes should thus be straightened up to be aligned in order to correct the rotation of the vertebrae, to correct the deformation of the spinal column.
The present invention more specifically relates to the basic correction principle defined, for example, in “SPINE” review, Volume 33, 2008 N° 14, pages 1588 to 1597, which principle has been protected by a patent, as appears from the teachings of document WO 2006/104813.
Mainly, rods are engaged through the different tubes by being progressively displaced from top to bottom to substantially align said tubes corresponding to the spinal column correction.
According to the state of the art, the tubes are fastened inside of the heads to enable the vertebrae to rotate, but do not enable to implant the final correction rod intended to connect, as indicated, the pedicle screw heads.
Indeed, according to the state of the art, after having lowered the rods introduced through several tubes, substantially perpendicularly to their generatrix, to achieve the alignment, the operator is forced to go to the other side of the spine, for example, on the concave side, if he has started the operation on the convex side. Once the implantable rod has been attached on the concave side, the operator has to disassemble the tubular elements to attach the implantable rod on the convex side.
It is thus necessary to operate in several steps, which has disadvantages. Indeed, the resulting loss of time, the need to assemble the implantable rod on the side opposite to that receiving the instruments for correcting the spine, causes a loss of correction.
The invention aims at overcoming these disadvantages in a simple, sure, efficient, and rational way.
The problem that the invention aims at solving is to be able, in one go, to intervene on one side of the column, for example, on the convex side, and then on the other side of the column, on the concave side, while carrying the double function of, on the one hand, straightening up the spinal bodies by means of tubular elements and, on the other hand, positioning the implantable rod and attaching it at the level of the pedicle screw heads, without having to disassemble said tubular elements, while aiming at determining the thoracic kyphosis-type curvature to be restored, in a sagittal plane.